This application claims priority from Japanese patent application Serial no. 2001-177895 filed Jun. 13, 2001, the contents of which are incorporated by reference herein.
1. Field of the Invention
The present invention relates generally to a control system for a rotary press, and more particularly to a control system for the so-called shaft-less rotary press that carries out printing operation by separately driving the driven components thereof, such as a printing section and a folding section, with independent motors; the control system capable of decelerating the driven components at least in synchronization with each other, and stopping them in the event of a main power failure.
2. Description of the Related Art
Conventional rotary presses, such as disclosed in Japanese Published Examined Patent Application No. Sho-60(1985)-36946, employ an integrated drive source comprising a plurality of main motors provided on a printing section, a folding section and other components of the rotary press connected to each other via a main shaft and a clutch to drive the entire rotary press system.
In recent years, on the other hand, the so-called shaft-less rotary press has become widely used due to various advantages in printing operation. In the shaft-less rotary press, a plurality of motors separately drive different driven components, with electrical synchronous control maintained so that the rotational speed and phase of the motors and the driven components can be properly matched with each other, as disclosed in Japanese Patent Publication Nos. 3037650 and 3059081.
With the shaft-less rotary press, however, the motors and the driven components tend to keep rotating by reason of inertia in case power feeding is interrupted due to a main supply failure during printing. This could lead not only to improper printing results but also to uneven tension on the paper web traveling in the rotary press, resulting in the breakage of the web or the clinging of the web around the rotary parts in extreme cases.
Restoration of the rotary press to the normal printing state, such as removal of the paper clung to the rotary parts, or rethreading of the web to the normal travel path, would take much time, preventing printing operation from being immediately resumed even after power supply has been returned to normal. This has been a big problem to be solved especially in newspaper printing and other printing operations requiring quick and timely printing.
As a measure to solve this problem, the shaft-less rotary press disclosed in Japanese Patent Publication No. 3037650 employs a construction where driven components are individually braked to stop the rotary press in case power feeding is interrupted due to a main power failure.
This rotary press control method, however, tends to have differences in the inertial forces that cause the driven components to keep rolling even after power feeding has been interrupted, and there are no small differences in braking forces to put brake on the rotation caused by the inertial forces. In addition, there is some time lag in the timing at which braking is started in each braking section. All these factors have caused variability in the time required for the rotating speed of each driven component to begin decreasing due to braking as well as in the time required for each driven component to come to a halt. For this reason, even this type of rotary press could not avoid uneven tensions on the traveling paper web in the rotary press that could lead to the breakage of the web or the clinging of the web around the rotary parts.
The present invention is intended to overcome the aforementioned problems, and it is therefore an object of the present invention to provide a rotary press control system, specifically for electrically synchronous-controlled shaft-less rotary presses, that is capable of control in the event of a power failure by preventing uneven tensions from exerting on a continuous paper web that travels in the rotary press, thereby preventing the paper web from breaking or sticking to the rotary parts, so that printing operation can be resumed immediately after the main power is restored.
The present invention provides a rotary press control apparatus capable of controlling, in the event of a power failure, the operation of a rotary press comprising at least one unit each of printing and folding sections; each of the printing and folding sections having at least one electric motor so as to be driven individually, the rotary press operated in a synchronized manner by the motors; the apparatus comprising: an inverter provided on each motor for controlling the rotation of the motor; a basic command output section that can be operated even in a power failure for outputting a normal operation basic speed command signal during normal operation, and a power failure basic speed command signal and a power failure basic voltage command signal for specifying the voltage of power fed to the inverter in the event of a power failure; a power failure detecting section for detecting a power failure and outputting a power failure signal; a power failure power feeding section for storing the power generated by the inertial rotation of the motors during a power failure where the power failure detecting section detects the power failure and feeding power to each of the inverters; and a control command output section that can be operated even in a power failure for outputting a normal operation control speed command signal in accordance with the normal operation basic speed command signal during normal operation, and in the event of a power failure where the power failure detecting section detects the power failure, comparing the power failure basic voltage command signal with an output voltage detection signal of the power failure power feeding section, and generating a power failure control speed command signal for output by correcting the power failure basic speed command signal in accordance with the comparison results, so that the rotary press can be decelerated and stopped at least in a synchronized state in the event of a power failure while stabilizing the voltage of the power fed to each of the inverters from the power failure power feeding section to a voltage level instructed by the power failure basic voltage command signal.
The present invention provides a rotary press control method capable of controlling, in the event of a power failure, the operation of a rotary press comprising at least one unit each of printing and folding sections; each of the printing and folding sections having at least one electric motor so as to be driven individually, and an inverter provided on each motor for controlling the rotation of the motor; the rotary press operated in a synchronized manner by the motors, the method comprising: a basic command output process that can be operated even in a power failure for outputting a normal operation basic speed command signal during normal operation, and a power failure basic speed command signal and a power failure basic voltage command signal for specifying the voltage of power fed to the inverter in the event of a power failure; a power failure detecting process for detecting a power failure and outputting a power failure signal; a power failure power feeding process for storing the power generated by the inertial rotation of the motors during a power failure where the power failure detecting process detects the power failure and feeding power to each of the inverters; and a control command output process that can be operated even in a power failure for outputting a normal operation control speed command signal in accordance with the normal operation basic speed command signal during normal operation, and in the event of a power failure where the power failure detecting process detects the power failure, comparing the power failure basic voltage command signal with an output voltage detection signal of the power failure power feeding process, and generating a power failure control speed command signal for output by correcting the power failure basic speed command signal in accordance with the comparison results, so that the rotary press can be decelerated and stopped at least in a synchronized state in the event of a power failure while stabilizing the voltage of the power fed to each of the inverters from the power failure power feeding process to a voltage level instructed by the power failure basic voltage command signal.
According to the present invention, the rotary press is controlled through the following operations.
In normal operation, electric power from a power supply is supplied to each motor after converted via the inverter serving the motor into an appropriate frequency to cause the motor to operate in accordance with the normal operation control speed command signal, and an appropriate power is also supplied via another path from the same power supply, or from another power supply, to the basic command output section and the control command output section.
The basic command output section outputs normal operation basic speed command signals on the basis of an instruction of a signal or a sequential signal given by manual operation via appropriate means in a state where power is supplied. The normal operation basic speed command signal thus generated is processed via the control command output section into a normal operation control speed command signal for output to the inverters.
Each inverter converts the power supplied from the power supply into an appropriate frequency to cause the motor which it controls to operate at an instructed speed specified by the input normal operation control basic speed command signal and output to the motor which the inverter controls in accordance with a predetermined processing for each inverter, so that the rotary press can operate at an operating speed specified by the input normal operation control speed command signal.
Each motor is rotated by the power of an appropriate frequency supplied via the corresponding inverter to drive each driven component.
In normal operating state, in case the power voltage drops due to a main power supply failure, a power failure detecting section detects it and outputs a power failure signal. As the power failure temporarily interrupts power feeding to the motor via the inverter, the motor begins inertial rotation, together with the driven component. Then, the emergency power supply begins supplying uniform power to each inverter, which in turn converts the uniform power into an appropriate frequency to cause the motor to operate in response to the power failure control speed command signal and supplies the power to the motor, and the power generated by the motor that keeps on inertial rotation is stored in the power failure power feeding section.
The power failure signal output by the power failure detecting section is fed to the basic command output section and the control command output section, both operable even during a power failure. Upon receipt of the power failure signal, the basic command output section changes the normal operation basic speed command signal that it has been outputting to a power failure basic speed command signal for output, and also outputs a new power failure basic voltage command signal. The power failure basic speed command signal instructs the rotary press to stop its operation after a predetermined deceleration process. Both the power failure basic speed command signal and the power failure basic voltage command signal output by the basic command output section are fed to the control command output section.
Both the power failure basic speed command signal and the power failure basic voltage command signal output by the basic command output section are correlated with each other for subsequent processing by the input power failure signal in the control command output section, which in turn processes both the power failure basic speed command signal and the power failure basic voltage command signal by correlating them with each other and generates a power failure control speed command signal for output to the inverters.
Each inverter converts the power fed from the power failure power feeding section into an appropriate frequency to cause the motor it serves to operate at a command speed given by the input power failure control speed command signal for output to the motor it controls in accordance with a predetermined processing procedures for each inverter, so that the rotary press can operate at an operating speed instructed by the input power failure control speed command signal, as in normal operation.
Each motor rotates in accordance with the power of an appropriate frequency to cause the motor to operate fed by the corresponding inverter. That is, when the inertial rotation of the motor is higher than the rotation in accordance with the frequency of the power fed by the inverter, the rotation of the motor is controlled by regenerative braking so as to match with the rotation in accordance with the frequency of the power fed by the inverter. When the inertial rotation of the motor is lower than the rotation in accordance with the frequency of the power fed by the inverter, on the other hand, the rotation of the motor is controlled so as to match with the rotation in accordance with the frequency of the power fed by the inverter. In either case, the motor decelerates and brings to a halt the driven component thereof in synchronization.
In this power failure control mode, the voltage of the power fed to the motor via the inverter is maintained at a stabilized state since the power failure control speed command signal is generated by correcting the power failure basic speed command signal on the basis of the power failure basic voltage command signal.